Shafer returns the grape pomace (by-product of the winemaking process) to the vineyards as a natural fertilizer. Recycling the grape pomace in the fields adds to the ecological efficiency of winemaking. Spread across the vineyards in the fall, it increases the organic and humus content of the soil, reducing the need for synthetic fertilizers. Essential nutrients are released into the soil gradually.

In contrast, commercial fertilizers tend to shock the vines with a heavy dose that cannot be readily absorbed. The application of grape pomace also invigorates the soil microbe population, which is vital to cover crop degradation.